1. Field of the Invention
The present invention relates to a universal joint for use in a leash for dogs. The joint head of the universal joint is of a ball shape and a retaining tube having a chamber provided with dome shaped end for housing the ball-shaped joint head is used so as to make the universal joint operated in a smoother manner, reducing frictional contact in rotation and preventing the roundly cornered chamber from damage of abrasion in use. In addition, the retaining hook will not be outwardly bent at corners. Such a universal joint is operated in wider angles and more smoothly.
2. Prior Art
Referring to FIGS. 1, 2, a first prior art universal joint applied to a leash which is made up of a hook 10, a retaining ring 20 and a leash element 90 is shown. The hook 10 has an extended rod 101 which terminates in an enlarged limiting cylinder 102. The closed retaining ring 20 has a locking element 201 having a round open-ended cavity 202 in which the limiting cylinder 102 is housed. In assembly, the enlarged limiting cylinder 102 is led through the open-ended cavity 202, then the locking element 201 of the retaining ring 20 is punched into an oval shape to rotarily secure the hook 10 to the retaining ring 20.
Such a prior art structure has the following disadvantages:
1. The friction between the locking element 201 and the limiting cylinder 102 is relatively serious, preventing smooth operation of the retaining ring 20 in use when the leash is subject to a strong pull. PA0 2. The open-ended cavity 202 of the retaining ring 20 is easily worn out due to abrasion, resulting in easy detachment of the retaining ring 20 from the enlarged limiting cylinder 102 of the hook 10. PA0 3. When the leash 90 and the retaining ring 20 is not placed in a rectilinear relation, the retaining ring 20 is easily bent, making smooth operation of the retaining ring 20 impossible.
Referring to FIGS. 3, 4, the second prior art is made up of a hook 30, a connector 40, a pair of pins 50, a sleeve 51 and a leash 90. The hook 30 has an engaging section 31 provided with a central round cavity 32 and a pair of symmetric pin holes 33. The connector 40 has an extended rod 41 which is provided with a deep central hole 42 at one end and an enlarged cylinder 43 at the other end. The sleeve 51 has a through hole 511 and a stop flange 512 in the interior and a peripheral groove 513 on the external surface.
The connector 40 is inserted into the sleeve 51 with the enlarged cylinder 43 engaged with the stop flange 512 and the extended rod 41 exposed externally of the through hole 511 in assembly. Then, the sleeve 51 is placed in the central round cavity 32 of the hook 30 with the peripheral groove 513 in line with the pin holes 33 so that the sleeve 51 can be retained in place in the central round cavity 32 of the hook 30, as shown in FIG. 4. In such a manner the connector 40 is safely and rotarily engaged with the sleeve 51. At last, the frontmost end of the leash 90 is placed in the central hole 42 and the extended rod 41 is punched to deform for fixing purpose. In common, such a prior art has the same disadvantages as the first one in practical operation.